1. Field Of The Invention
The field of art to which this invention pertains includes a control valve means for operating a lock-up clutch associated with a torque converter in a vehicle drive system wherein the torque converter couples the prime mover with a transmission. More particularly, the control valve means are adapted to regulate engagement and disengagement of the clutch with respect to prime mover rotational speed within a predetermined speed range.
2. Description Of The Prior Art
A torque converter, of course, serves to fluidically couple the prime mover with the transmission. However, in order to permit the bypassing of the fluid drive and to establish a more efficient direct mechanical drive between the prime mover and the transmission, when operationally feasible, a lock-up clutch is couplingly interposed between the torque converter input and output members. It is desirable to vary the degree of engagement of the lock-up clutch with respect to prime mover rotational speed in order to maintain prime mover rotational speed within its most favorable torque range. Therefore, below this desired torque range, the lock-up clutch is fully disengaged, while above this range it is fully engaged and within the range it is modulated therebetween.
Examples of prior art patents that disclose lock-up clutch control valves include U.S. Pat. Nos. 3,857,302 to Morris; 3,985,046 to Morris et al; 3,949,847 to Hoehn; 3,390,594 to Gillespie; and 3,897,698 to Ohsaka.